44° 



BELL 



homologous linear dimensions. Dr. Bell did not deny the law, as a 

 chagrined or an angry person might ; but, like a shrewd man of affairs, 

 he admitted the law, and discovered a way to evade it. 



Now that his reply is familiar to us, it may seem amusing that 

 people urged the Euclidean objection so strongly ; but the fact is that 

 many persons, besides Professor Newcomb, advanced it as an argument 

 against the practicability of mechanical flight. In the middle eighties 

 an eminent geologist made it the basis of a magazine article, in which he 

 proved, with fine eloquence, that it is impossible for a human being 

 ever to fly. He further supported his contention by a vigorous biolog- 

 ical argument, and possibly also by a theological or teleological one, I 

 do not remember. He asserted that nature had tried for centuries to 

 produce a flying creature as heavy as a man, but had failed ; therefore, 

 it is utterly impossible for man to achieve mechanical flight. By 

 diligent experimentation she had tested and adopted the strongest 

 possible materials, she had developed the most powerful motor for a 

 given weight, she had employed the most favorable shapes and the 

 most efficient mode of propulsion. But what was the outcome ? Her 

 largest flyer weighs hardly so much as a human dwarf. The ostrich 

 is the limit. The ostrich is the living witness of nature's failure. And 

 that picturesque old reptile, with the twenty-foot wings, that soared so 

 grandly over the Cretacean seas, remains to-day the fossil proof of 

 nature's utmost capacity, and therefore also of man's. Such argumentst 

 such prettily woven sophistries, such quaint immemorial cobwebs, have 

 Dr. Bell and his associates brushed reverently from the pages of science. 



There are many features of Dr. Bell's remarkable kites, both struc- 

 tural and aerodynamic, that merit most careful attention ; more parti- 

 cularly the relation of the forward resistance to the total upward lift, 

 the effectiveness of the provision for automatic stability and equilibrium 

 in all kinds of tumultuous winds, the distribution of stresses in the frame, 

 and of the impulsive pressures over the sustaining surfaces. But these 

 topics seem to me more suitable for experimentation than for abstrac, 

 analysis. 



One interesting phenomenon, however, I will notice in closing. 

 Dr. Bell relates that his floating kites, which in calm weather, could 

 advance but four miles an hour, still continued to make headway 

 against a sixteen-mile wind. The momentum of the craft might main- 

 tain this forward motion for a few seconds, but not for a considerable 

 period. For the total momentum in any direction is equal to the initial 

 momentum plus the impulse of the resultant force in the line of pro- 

 gression. Or, in the language of algebra, 



